Administration set detection and authentication using cam profiles

ABSTRACT

An administration set for an infusion pump includes a free-flow prevention device having a movable plunger that includes a cam surface defining an uneven profile along a direction of movement of the plunger, wherein the shape of the cam surface profile indicates the administration set is authorized for use with the infusion pump and may further indicate the specific type of administration set. A sensor in the infusion pump senses movement of the plunger as a platen of the infusion pump is latched and generates a profile signal in the time domain representative of the cam surface profile. A processor evaluates the profile signal and controls operation of the pump to protect a patient from improper loading of an administration set, use of an unauthorized administration set, and/or use of an invalid type of administration set for a chosen infusion protocol.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a division of co-pending U.S. applicationSer. No. 15/243,438 filed Aug. 22, 2016, the entire disclosure of whichis hereby incorporated by reference in the present application.

FIELD OF THE INVENTION

The present invention relates generally to infusion pumps for controlleddelivery of liquid food and medications to patients. More specifically,the present invention relates to a sensor system for detecting whetheror not an administration tubing set is operatively connected to aninfusion pump.

BACKGROUND OF THE INVENTION

Programmable infusion pumps are used to carry out controlled delivery ofliquid food for enteral feeding and medications for various purposes,for example pain management. In a common arrangement, an infusion pumpreceives a disposable administration set comprising flexible tubinghaving a tubing segment designed to be engaged by a pumping mechanism ofthe infusion pump. The administration set may further comprise a pair ofmounting components fixedly attached to the flexible tubing atpredetermined locations at or near opposite ends of the tubing segment,whereby the mounting components are receivable by respective matingfeatures on the infusion pump to secure the tubing segment in properposition for operative engagement by the pumping mechanism. One of themounting components may provide additional functionality beyond helpingto properly locate the tubing segment. For example, one of the mountingcomponents may be configured as a free-flow prevention device operableto selectively stop and permit flow of the infusion liquid through thetubing. Upon loading the administration set in the pump, the free-flowprevention device is actuated from its normal flow-stopping closedposition to its open position allowing flow. An example of thearrangement described above is disclosed in U.S. Pat. No. 6,164,921 toMoubayed et al.

It is known to provide different types of administration sets all ofwhich are intended for use with a particular infusion pump model ormodels. The various types of administration sets may be distinguishablefrom one another according to design specifications that are chosenbased on the specific intended use of the administration set. Forexample, the tubing segment of the administration set may be dimensionedwith a specific inner diameter and wall thickness for carrying certainliquid formulations of known viscosity, and may be formed of a materialhaving a specific durometer. The material durometer, inner diameter, andwall thickness of the tubing segment are held within close manufacturingtolerances to ensure that the administration set provides intended flowcharacteristics when the tubing segment is acted upon by the pumpingmechanism of the infusion pump.

Various types of administration sets may also be distinguishable fromone another based on coupling hardware and other structural featuresprovided as part of the administration set. For example, an end of theadministration set may be provided with a bag for storing liquid, avented vial spike, or a non-vented spike. As another example, theadministration set may include a filter of a predetermined pore size, orit may not include a filter. Other structural features that may or maynot be included in a particular administration set are an anti-siphonvalve and a Y-connector having a check valve.

For safety reasons, it is desirable to ensure that the type ofadministration set chosen for use with a particular infusion pump todeliver an intended infusion protocol is the proper administration set.As an initial matter, it is desirable to confirm that an administrationset is installed in the infusion pump. The installed administration setshould be authentic from the standpoint that it is approved by theinfusion pump manufacturer for use with the infusion pump. The installedadministration set should also be of a type that is configured fordelivering a selected infusion protocol which the infusion pump isprogrammed to execute.

What is needed is an administration set detection and authenticationscheme that is easily implemented without adding hardware to theadministration set or the infusion pump, that determines whether or notan administration set is installed and is authentic, and thatdistinguishes among different types of authentic administration sets toidentify the type of administration set that is installed.

SUMMARY OF THE INVENTION

In accordance with the present invention, a free-flow prevention devicefor controlling flow of an infusion liquid through tubing of anadministration set comprises a movable plunger that includes a camsurface defining an uneven profile along a direction of movement of theplunger, wherein the shape of the cam surface profile indicates theadministration set is authorized for use with the infusion pump and mayfurther indicate the type of administration set.

A sensor in the infusion pump is arranged to sense movement of theplunger as a platen of the infusion pump is latched thereby moving theplunger from a closed position to an open position. As the plunger ismoved, the cam surface of the plunger displaces a follower in contactwith the cam surface, and the sensor detects displacement of thefollower to generate a profile signal in the time domain representativeof the cam surface profile.

A processor compares the profile signal to stored reference valuescorresponding to various predetermined authorized profiles, anddetermines whether or not the administration set is loaded in theinfusion pump and whether or not the administration set is authorizedfor use with the infusion pump. If the administration set is notproperly loaded or is not authorized, the processor sends a commanddisabling operation of the infusion pump. The processor may alsodetermine the specific type of the administration set from among aplurality of administration set types, and send a command disablingoperation of the pump if the determined type of the administration setis incompatible with a desired infusion protocol entered into theinfusion pump by a user.

BRIEF DESCRIPTION OF THE DRAWINGS

The nature and mode of operation of the present invention will now bemore fully described in the following detailed description of theinvention taken with the accompanying drawing figures, in which:

FIG. 1A is perspective view of an infusion pump formed in accordancewith an embodiment of the present invention, wherein a front cover ofthe infusion pump is removed to reveal internal structure;

FIG. 1B is a view showing an administration set formed in accordancewith an embodiment of the present invention for use in the infusion pumpshown in FIG. 1A;

FIG. 2 is another perspective view of the infusion pump andadministration set shown in FIG. 1, however a platen of the infusionpump is shown in an open position for loading or unloading theadministration set;

FIG. 3 is a detailed perspective view showing a free-flow preventiondevice of the administration set received by the infusion pump;

FIG. 4A is a front elevational view showing the administration set andan upper pumping mechanism of the infusion pump, wherein the platen isin the open position and a locking latch associated with the platen isin an unlocked position;

FIG. 4B is a view similar to that of FIG. 4A, wherein the platen ispivoted toward a closed position and the locking latch is partiallypivoted from the unlocked position toward the locked position;

FIG. 4C is a view similar to that of FIG. 4B, wherein the platen ispivoted into the closed position and the locking latch is fully pivotedinto the locked position;

FIG. 5 is an exploded perspective view of the free-flow preventiondevice of the administration set;

FIG. 6A is an elevational view of the free-flow prevention devicelooking axially along tubing of the administration set, wherein aplunger of the free-flow prevention device is in a closed positionrelative to a carrier of the free-flow prevention device;

FIG. 6B is a view similar to that of FIG. 6A, wherein the plunger ismoved relative to the carrier away from the closed position and towardan open position;

FIG. 6C is a view similar to that of FIG. 6B, wherein the plunger is inthe open position relative to the carrier;

FIG. 7A is an elevational view showing the plunger operatively connectedto a sensor of the pump by a follower, wherein the plunger is in theclosed position and has a first cam surface profile;

FIG. 7B is a view similar to that of FIG. 7A, wherein the plunger ismoved away from the closed position and toward the open position, andthe follower is displaced laterally to deform the sensor;

FIG. 7C is a view similar to that of FIG. 7B, wherein the plunger ismoved into the closed position, and the follower is further displacedlaterally to further deform the sensor;

FIG. 8 is a plot showing amplitude versus time of a signal generated bythe sensor in FIGS. 7A-7C;

FIG. 9 is an elevational view of another plunger having a second camsurface profile differing from the first cam surface profile;

FIG. 10 is a plot showing amplitude versus time of a sensor signalresponsive to movement of the plunger shown in FIG. 9 from the closedposition to the open position;

FIG. 11 is an elevational view of yet another plunger having a third camsurface profile differing from the first and second cam surfaceprofiles;

FIG. 12 is a plot showing amplitude versus time of a sensor signalresponsive to movement of the plunger shown in FIG. 11 from the closedposition to the open position;

FIG. 13 is a schematic diagram showing signal processing electronics ofthe infusion pump shown in FIG. 1; and

FIG. 14 is a flow diagram showing decision logic executed by the signalprocessing electronics in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1A shows an infusion pump 10 and FIG. 1B shows a disposableadministration set 12 designed to be removably received by infusion pump10. Administration set 12 comprises tubing 14 for conveying an infusionliquid, and a free-flow prevention device 16 operable to selectivelystop and permit flow of the infusion liquid through the tubing 14.Administration set 12 may also comprise a locator pin 18. Free-flowprevention device 16 and locator pin 18 may be fixedly attached totubing 14 at separate locations along the tubing. For example, free-flowprevention device 16 and locator pin 18 may be bonded to tubing 14 by abonding agent. As may be seen in FIG. 1A, infusion pump 10 has a firstrecess 20 sized to removably receive free-flow prevention device 16, anda second recess 22 sized to removably receive locator pin 18.Administration set 12 is loaded into infusion pump 10 by insertingfree-flow prevention device 16 into first recess 20 and locator pin 18into second recess 22 such that a segment 15 of tubing 14 wraps around apumping mechanism 24 of pump 10. Free-flow prevention device 16 mayinclude a breakaway detent tab 17 for maintaining free-flow preventiondevice 16 in an open condition prior to loading of administration set 12in pump 10. In the illustrated embodiment, pumping mechanism 24 is aperistaltic pumping mechanism having a plurality of extendable andretractable pumping fingers 26 that are moved by rotation of amotor-driven eccentric cam 28 to engage tubing segment 15 in sequentialperistaltic fashion such that liquid is pumped through tubing 14.

As may be seen in FIG. 2, infusion pump 10 includes a platen 30pivotally mounted at a pivot pin 32. Platen 30 has a platen surface 30Athat comes into contact with tubing segment 15 opposite pumping fingers26 when platen 30 is pivoted down toward pumping mechanism 24. A lockinglatch 34 is pivotally mounted at a free end of platen 30 by a pivot pin36. As will be described in detail below, locking latch 34 is operableto secure platen 30 in a closed position on infusion pump 10 with platensurface 30A contacting tubing segment 15 in preparation for starting apumping protocol. Locking latch 34 further serves as an actuating memberfor moving a plunger 38 of free-flow prevention device 16, visible inFIG. 3, relative to a carrier 40 of free-flow prevention device 16.

FIGS. 4A-4C illustrate closure of platen 30 and operation of lockinglatch 34 after administration set 12 is positioned in pump 10. Platen 30is pivoted counterclockwise until a drive arm 42 of locking latch 34contacts a top portion of plunger 38, and then locking latch 34 ispivoted clockwise relative to platen 30 such that a curved surface 44 atthe end of drive arm 42 forces plunger 38 to move downward relative tocarrier 40. As locking latch 34 is pivoted, a jaw opening 46 on eachside of the locking latch securely mates with a corresponding lateralprotrusion 48 of the infusion pump body to lock platen 30 in its closedoperating position.

In accordance with the present invention, the movement of plunger 38 issensed in the time domain and provides information for detecting andauthenticating administration set 12. In an embodiment of the invention,plunger 38 includes a cam surface 50 defining an uneven profile along adirection of movement of the plunger, wherein the uneven profile of camsurface 50 indicates that administration set 12 is authorized for usewith infusion pump 10, and further indicates the type of administrationset 10. The basic operation of free-flow prevention device 16 may beunderstood from FIGS. 5 and 6A-6C. Plunger 38 is mounted in carrier 40for sliding reciprocal motion relative to the carrier between a closedposition (FIG. 6A) in which respective tube openings in the plunger andcarrier are misaligned to pinch tubing segment 15 closed to prevent flowthrough tubing 14, and an open position (FIG. 6C) in which respectivetube openings in the plunger and carrier are substantially aligned sothat tubing segment 15 is not pinched closed and flow is permittedthrough tubing 14. A spring 39 acts between carrier 40 and plunger 38 tobias plunger 38 toward the closed position shown in FIG. 6A. As may beunderstood, plunger 38 must be moved against the biasing force of spring39 to move plunger from the closed position to the open position. Asexplained above with reference to FIGS. 4A-4C, such force is provided bypivoting locking latch 34 relative to platen 30 so that curved surface44 at the end of drive arm 42 moves plunger 38 downward relative tocarrier 40. Plunger 38 is held in the open position when platen 30 issecured by locking latch 34. When locking latch 34 is pivotedcounterclockwise in FIG. 4C to allow platen 30 to be opened, plunger 38is allowed to move under force of spring 39 to the closed position toprevent free flow. In addition to the basic operation of free-flowprevention device 16, the movement of plunger 38 provides a detectablesignature that depends on the profile of the plunger's cam surface 50.

Infusion pump 10 comprises a sensor 52 arranged to sense the movement ofplunger 38 relative to carrier 40. Sensor 52 generates a profile signalin the time domain representative of the profile of cam surface 50. Inan embodiment of the invention illustrated by FIGS. 7A-7C, sensor 52 maybe a strain gauge and infusion pump 10 may comprise a follower 54 biasedfor continuous engagement with cam surface 50 of plunger 38 whenfree-flow prevention device 16 is loaded in the infusion pump, whereincam surface 50 slidably engages follower 54 to displace the followerlaterally as plunger 38 is moved from the closed position to the openposition. Sensor 52 has one end portion attached by a fastener 56 to afixed structural member of pump 10 (not shown), and another end portionengaged by follower 54, such that lateral displacement of follower 54causes corresponding deflection of sensor 52. Sensor 52 and follower 54may be arranged such that sensor 52 is slightly deflected even whenplunger 38 is in the closed position represented by FIGS. 6A and 7A,such that a preload is applied by sensor 52 on follower 54 to maintainengagement of the follower with cam surface 50. The output signalgenerated by sensor 52 is proportional to the amount of deflection ofthe sensor. The behavior of the signal generated by sensor 52 in thetime domain will depend on the profile shape of cam surface 50. Thus, byproviding various predetermined profiles of cam surface 50 that share atleast one feature among all profiles and differ from one another withrespect to at least one other feature, the cam surface profiles may beused to confirm authenticity of an administration set 12 as beingcompatible with pump 10, and also to determine the specific type of theadministration set from among a plurality of different administrationset types all of which are compatible with pump 10.

In FIGS. 7A-7C, the profile of cam surface 50 includes a first plateau58 and a second plateau 60 having different respective “elevations” E1and E2. As used herein in reference to the profile of cam surface 50,the term “elevation” means a lateral distance from a central axis 41along which plunger 38 moves. First plateau 58 and second plateau 60 mayhave different respective lengths L1 and L2 in the direction of movementof plunger 38. The profile of cam surface 50 may further include atopographical feature 62 between first plateau 58 and second plateau 60.In the embodiment shown in FIGS. 7A-7C, topographical feature 62 takesthe form of a ramp between first plateau 58 and second plateau 60.Topographical feature 62 may take other forms, for example a bump or arecess.

FIG. 8 shows a voltage signal 64 versus time generated by sensor 52 inresponse to the downward motion of plunger 38 depicted by FIGS. 7A-7C.As may be seen, signal 64 has a first portion 66 of relatively lowamplitude corresponding to first elevation E1, and a second portion 68of relatively high amplitude corresponding to second elevation E2.Signal 64 also includes a transition portion 67 between first and secondportions 66 and 68 characterized by changing amplitude.

FIG. 9 shows an alternative plunger 138 having another possible profileof cam surface 50. In plunger 138, the topographical feature 62 of camsurface 50 is a bump that rises in elevation and then drops downslightly as it transitions from first plateau 58 to second plateau 60.First plateau 58 has the same elevation E1 as that of the plunger 38shown in FIGS. 7A-7C, however second plateau 60 has a differentelevation E3 that is slightly less than the elevation E2 of plunger 38.FIG. 10 illustrates a voltage signal 164 versus time generated by sensor52 in response to the downward motion of plunger 138. A first portion166 of sensor signal 164 has the same amplitude as the first portion 66of sensor signal 64 due to matching elevations of the first plateaus 58.A second portion 168 of sensor signal 164 has an amplitude greater thanthe amplitude of first portion 166, but less than the amplitude ofsecond portion 68 of signal 64, owing to the fact that elevation E3 isless than elevation E2. A transition portion 167 of signal 164 ischaracterized by a significant increase in amplitude followed by amodest decrease in amplitude as determined by bump 62 in cam surface 50of plunger 138.

FIG. 11 shows a further alternative plunger 238 having yet anotherpossible profile of cam surface 50. In plunger 238, the topographicalfeature 62 of cam surface 50 is a bump that rises in elevation and thendrops down significantly as it transitions from first plateau 58 tosecond plateau 60. First plateau 58 has the same elevation E1 as that ofthe plungers 38 and 138, however second plateau 60 has a differentelevation E4 that is less than elevation E2 of plunger 38 and elevationE3 of plunger 138. FIG. 12 illustrates voltage signal 264 versus timegenerated by sensor 52 in response to the downward motion of plunger238. A first portion 266 of sensor signal 264 has the same amplitude asthe first portions 66 of sensor signals 64 and 164 due to matchingelevations of the first plateaus 58. A second portion 268 of sensorsignal 264 has an amplitude greater than the amplitude of first portion266, but less than the amplitude of second portion 168 of signal 164because elevation E4 is less than elevation E3. A transition portion 267of signal 264 is characterized by a significant increase in amplitudefollowed by a decrease in amplitude as determined by bump 62 in camsurface 50 of plunger 238.

Thus, signals 64, 164, and 264 corresponding to plungers 38, 138, and238 share similar signal portions, but are distinguishable from oneanother by other signal portions exhibiting different amplitudes andbehaviors in the time domain. The similar signal portions may be used todetermine the presence and authenticity of an administration set,whereas the different signal portions may be used to determine thespecific type of administration set from a plurality of authenticadministration sets authorized for use with infusion pump 10.

FIG. 13 is a schematic diagram showing signal processing electronics ofinfusion pump 10 used to evaluate profile signals generated by sensor52. An analog signal from sensor 52 is converted to a digital signal byan analog-to-digital converter 70 and stored in a volatile memory 71.The digitized signal is then read by a processor 72 programmed toevaluate the signal. Processor 72 executes programming instructionsstored in a non-volatile memory 74 associated with the processor 72.Memory 74 also stores predetermined reference values representing thevarious respective profile signals of each type of authorizedadministration set. The reference values may be stored, for example, ina lookup table that provides expected amplitude values at predeterminedmoments in time for each profile signal. Processor 72 executesprogramming instructions stored in memory 74 causing the processor tocompare the digitized profile signal from sensor 52 to the storedreference values and determine whether or not the administration set isloaded in the infusion pump, and whether or not the administration setis authorized for use with the infusion pump, based on the comparison.Processor 72 may be in communication with a pump controller 76, or mayitself act as the pump controller, whereby operation of pump 10 may becontrolled based on an evaluation of the profile signal generated bysensor 52. Pump controller 76 is in communication with a user interfacedisplay screen 78 and a keypad 80 for inputting commands and parametersto the controller.

The flow diagram of FIG. 14 shows, in accordance with an embodiment ofthe invention, decision logic executed by processor 72 and/or controller76 to evaluate a profile signal and control infusion pump 10 based onresults of the evaluation. In block 82, the digitized profile signalstored in memory 71 is read by processor 52. A first comparison isperformed in block 84 looking at a portion of the signal used toindicate presence and authenticity of an administration set. Forexample, a comparison of first portion 66, 166, 266 of the signal tocorresponding stored reference values may be conducted. In decisionblock 86, flow branches based upon whether the comparison finds a match.If a match is not found, the administration set is determined to beimproperly loaded and/or inauthentic, and flow is directed to blocks 88and 90 to display an error message on display screen 78 and commandcontroller 76 to disable operation of pump 10. Thus, the patient isprotected from improper loading of an administration set even if theadministration set is authorized, and the patient is also protected fromuse of an unauthorized administration set. If a match is found in block86, then the administration set is deemed to be properly loaded andauthentic, and flow continues to block 92.

In block 92, a further comparison is performed looking at a portion ofthe profile signal used to indicate the specific type of administrationset. For example, a comparison of second portion 68, 168, 268 of thesignal to corresponding stored reference values, and/or a comparison oftransition portion 67, 167, 267 of the signal to corresponding storedreference values may be conducted. In decision block 94, flow branchesbased upon whether the further comparison finds a matching type. If amatch is not found, the administration set is determined to beimproperly loaded and/or inauthentic, and flow is directed to blocks 88and 90. If a match is found in block 94, the correspondingadministration set type is identified and reported as a parameter topump controller 76 in accordance with block 96.

Pump controller 76 may be programmed to operate in a predeterminedmanner based on the identified type of administration set and aninfusion protocol entered in pump 10 by a user. For example, in block98, the identified type of administration set may be checked against apredetermined list of valid set types associated with the enteredinfusion protocol and stored in memory 74. In decision block 100, flowbranches based upon whether or not the administration set type is validfor the selected infusion protocol. If not, flow is directed to block 88to display an error message on display screen 78 indicating theadministration set is the wrong type, and then to block 90 to disableoperation of pump 10. If the detected administration set type is validfor use in delivering the selected infusion protocol, then pumpoperation continues in a normal manner. Thus, the present inventionprotects the patient if the wrong type of administration set is loadedfor a desired infusion protocol, even if the administration set isauthentic.

Comparisons between the sensed profile signal and the storedpredetermined reference values representing various recognized profilesignals may be made in different ways. Amplitude values of the sensedprofile signal may be sampled at predetermined times and compared tocorresponding stored values. Comparisons may also involve determining atime duration that the sensed profile signal remains at a givenamplitude level before the amplitude changes, and comparing suchduration to an expected duration represented by the stored referencevalue information. For this type of comparison, it is helpful to designlocking latch 34 and free-flow prevention device 16 such that plunger 38moves at a substantially fixed velocity relative to carrier 40 so thatthe time duration is indicative of the plateau length L1 or L2 in thedirection of movement of plunger 38. A first time interval T1 of theprofile signal may be evaluated to determine whether or not theadministration set is loaded and is authorized, and a second timeinterval T2 of the profile signal different from the first time intervalT1 may be evaluated to determine the type of the administration set. Asshown in FIG. 8, the first and second time intervals T1 and T2 mayoverlap one another, but this is an option, not a requirement.

Comparisons may involve some portions of the sensed profile signal,while disregarding at least one other portion of the profile signal. Forexample, a spike or dip in the amplitude of the profile signal at thetransition portion 67 due to a bump or recess in cam surface 50 may beused as a primary comparison feature, a secondary comparison feature forconfirmation, or not at all. Evaluation logic may also be “single step”in nature, whereby the entire sensed profile signal is compared tostored reference values to find a complete match; if no match is found,an error message is displayed and the pump is disabled. If a match isfound, the administration set type is known and can be validated withrespect to an entered infusion protocol. As will be understood,evaluation of a sensed profile signal, and logic implemented based onthe evaluation, are subject to wide design variation.

The particular configuration of sensor 52 is also subject to designchoice. While a strain gauge is illustrated in the drawings, sensor 52may be a magnetic or capacitive displacement sensor, an opticaldisplacement sensor, or an acoustic displacement sensor. Any type ofsensor capable of measuring displacement of follower 54 may be used inpracticing the present invention.

While the invention has been described in connection with exemplaryembodiments, the detailed description is not intended to limit the scopeof the invention to the particular forms set forth. The invention isintended to cover such alternatives, modifications and equivalents ofthe described embodiment as may be included within scope of the claims.

What is claimed is:
 1. A free-flow prevention device for controllingflow of an infusion liquid through tubing of an administration set foruse with an infusion pump having a follower, the free-flow preventiondevice comprising: a carrier; a plunger movable relative to the carrierbetween an open position permitting flow of the infusion liquid throughthe tubing and a closed position stopping flow of the infusion liquidthrough the tubing; and a spring biasing the plunger toward the closedposition; wherein the plunger includes a cam surface defining an unevenprofile along a direction of movement of the plunger; wherein the camsurface is exposed through a slot in the carrier and is slidablyengageable by the follower, and the cam surface profile is configured todisplace the follower in an elevation direction orthogonal to thedirection of movement of the plunger as the plunger is moved from theclosed position to the open position.
 2. The free-flow prevention deviceaccording to claim 1, wherein the cam surface profile includes a firstplateau and a second plateau having different respective elevations. 3.The free-flow prevention device according to claim 2, wherein the firstplateau and the second plateau have different respective lengths in thedirection of movement.
 4. The free-flow prevention device according toclaim 2, wherein the cam surface profile further includes atopographical feature between the first plateau and the second plateau.5. The free-flow prevention device according to claim 4, wherein thetopographical feature is a bump, a ramp, or a recess.